This may result in the death of many organisms such as fish that require oxygen.

It is the first animal species to be named that does not require oxygen at any point during its life.

When the heart muscle has to work harder, such as during exercise, it requires more oxygen.

To be effective, the biota require both oxygen and food to live.

But they may require oxygen while walking, exercising or during sleep.

This reduces the work of the heart so that it requires less blood and oxygen.

It requires oxygen to breathe, so breaks the surface at least once every six hours.

Exercise makes the heart muscle work harder, which in turn requires more oxygen.

Nuclear reactions do not require oxygen to run, just fuel and energy.

When the heart does not have to work as hard, it requires less oxygen.